Cardisoma armatum are more commonly known as Rainbow Crabs, Patriot Crabs, Tricolor Crabs, Moon Crabs or Soapdish Crabs.

Rainbow Crabs are a popular group of semi-terrestrial crabs.

They are hardy and easy to care for, making them a great choice for beginner aquarists.

Young and newly molted Rainbow Crabs are often very colorful with a purple-blue carapace and orange-red legs and tips of chelae. With age and approach to molt, carapace turns dirty yellow with occasionally slight reddish spots dorsally.

When they are young or when they have freshly molted their colors will be more vivid. As they age their colors will become lighter and more washed out.

Rainbow Crabs can grow pretty big in aquariums. Naturally, they reach 15 cm (6 inches) long, but they are likely to be nearer 7 – 12 (3 – 4 inches) when kept at home. The total weight can range between 96 – 290 g. Therefore, it will be better to give them extra space in your tank in case they grow a little larger than expected.

Rainbow Crabs have a lifespan of about 5 – 8 years